1. Field of the Invention
This invention relates to a headlight unit, and in particularly to a headlight unit for motor vehicles, such as cars, in which the high beam and the low beam are obtained by rotating a reflecting mirror.
2. Description of the Prior Art
In the case of car headlights, there is a requirement for switching between a high beam and a low beam, and two principal systems are used for this purpose.
One of these utilized a sealed beam type lamp in which two light sources are provided in conjunction with a reflecting mirror. When one of these light sources is operated, the low beam is generated, and when the other light source is operated or both light sources are operated at the same time, the high beam is generated. In this type lamp the beams are switched by switching the light sources.
In the other system, one light source is utilized with a reflecting mirror. The beam is switched by rotating the reflecting mirror or the light source, itself, upward and downward.
This invention relates to the latter system, the problems of which are discussed below.
In headlights which switch between low beam and high beam, the downward attitude of the reflecting mirror when the low beam is lit must be controlled with great accuracy to avoid blinding oncoming traffic. Previously, a vertical aiming bolt and a surrounding coil spring have been used to control the attitude of the reflecting mirror in the vertical direction. This bolt acts as a stopper, which controls the downward attitude position of the reflecting mirror. In addition, the spring is designed to permit the rotation of the reflecting mirror to allow upward rotation. Moreover, an actuator is used to make the reflecting mirror rotate upward and downward. Hitherto, solenoid systems, compressed gas systems, or motor drive systems have been used as actuators.
A headlight system which uses this kind of actuator with a vertical direction aiming bolt controls the downward attitude position of the reflecting mirror through the vertical aiming bolt, and determines the high beam direction by rotation of the reflecting mirror upward in response to the working stroke of the actuator.
Although this type of headlight is susceptible to errors such as errors in manufacture of the reflecting mirror, manufacturing errors and installation errors in the light source, and installation errors in the attitude of the reflecting mirror in the vehicle, adjustments to correct such errors can be carried out after installing the headlight on the vehicle body.
When making such adjustments, the position for the downward attitude of the reflecting mirror is determined by adjusting the vertical direction aiming bolt. Then, the upward position is adjusted by operating the actuator.
In the past a two-stage adjustment operation has been necessary for making this kind of adjustment. First, the position of the downward attitude of the reflecting mirror must be determined by the vertical aiming bolt. Then the rotation of the reflecting mirror must be adjusted by adjusting the working stroke of the actuator. These operations result in adjustment of the angles of dip and elevation of the low beam and the high beam, but the multistage process takes too long. In particular, during periodic maintenance including vertical aiming adjustment, the working stroke of the actuator also has to be readjusted, and this makes the work more complicated.
Moreover, the need for a vertical aiming bolt and spring increases the number of parts, and makes the assembly work more complicated.
The present invention provides a headlight unit of a simpler construction in which vertical aiming adjustments of the reflecting mirror and rotational adjustments of the reflecting mirror can be easily carried out and, at the same time, the need for a vertical aiming bolt and spring can be eliminated.